There’s a lot of hand-wringing about American students lagging their foreign counterparts in math skills. That should not be a big surprise, since many of our political leaders aren’t very good at math either and deny the realities that numbers reveal. Republican Sen. John McCain recently labeled the extreme hard-liners in his own party as “wacko birds,” but there are plenty of flaky fowl in Democratic ranks as well.

Start with the Republicans, whose statistical stupidity centers on electoral politics. A voting-age population that was 88 percent white when Ronald Reagan won the presidency in 1980 had dropped to 72 percent white last year, and that number will continue to decline. The GOP performed miserably with racial minorities in 2012, winning 6 percent of African-Americans, 26 percent of Asians and 27 percent of Latinos. Add a 37 percent showing among voters younger than 30, and the demographic trend is inescapable.

Some truth tellers are trying to force the party to face these grim facts. A report this week from the Republican National Committee stated bluntly: “Public perception of the party is at record lows. Young voters are increasingly rolling their eyes at what the party represents, and many minorities wrongly think that Republicans do not like them or want them in the country.”

At a press briefing on the report, party Chairman Reince Priebus focused on this critical calculation: “Party leaders have to constantly remind everybody that we can’t build a party by division and subtraction. We can only build the party by addition and multiplication.”

But the mathematical myopia gripping the GOP base was on full display last weekend at a big gathering in Washington called the Conservative Political Action Conference. The prevailing gospel seemed to be that Mitt Romney lost because he was not conservative enough. And in defiance of Priebus’ advice about the virtues of addition, the True Believers took exactly the opposite approach, urging the party to purge itself of any pragmatist who strays from theological orthodoxy.

Two Republican governors who have sinned by working with Democrats — Chris Christie of New Jersey and Bob McDonnell of Virginia — were not even invited to CPAC. In a speech, Sarah Palin lacerated Karl Rove, the GOP strategist who dares to suggest that the party must stop nominating unelectable hard-liners. A straw poll of convention-goers was won by Sen. Rand Paul of Kentucky, a serious candidate for president only to folks who failed third-grade arithmetic.

Former Sen. Rick Santorum spoke for many in the crowd when he denounced “those in our movement who want to abandon our moral underpinnings so we can win.” Funny, we always thought politics was about winning elections. But if the Republicans prefer martyrdom in the name of purity to victory, no one will cheer more loudly than the Democrats.

As for those Democrats, their addled arithmetic focuses mainly on entitlements such as Medicare and Social Security. The party’s “common sense caucus,” as President Obama calls its members, understands that current benefit levels are unsustainable and eventually will bankrupt the system. Moreover, the demands of an aging population will soak up a growing share of federal revenue and make it harder for progressives to afford critical investments in areas such as education, technology and medical research.

Sen. Mark Warner of Virginia recently warned fellow Democrats of this numerical nemesis: “The longer we put off this inevitable math problem, the longer we fail to come up with a way to make sure that the promise of Medicare and Social Security is not just there for current seniors but for those 30 years out.”

Obama has made it clear during recent visits to Capitol Hill that he is ready to consider entitlement reform as long as it is coupled with new revenues. But Democratic “wacko birds,” their heads planted firmly in the sand, are as mathematically challenged as their Republican counterparts. A majority of House Democrats have signed a letter declaring their “vigorous opposition” to any and all benefit reductions. Sen. Bernard Sanders of Vermont specifically rejected Obama’s views and embraced arithmetical ignorance: “Some of us believe very strongly that it would be absolutely wrong to cut Social Security benefits.”

A few final numbers: Last fall, 25 percent of all voters called themselves liberals, 35 percent said they were conservatives and 41 percent identified themselves as moderates. Clearly, neither side can win a majority by appealing solely to its base. Addition, not subtraction, is the only path to victory. But too many leaders in both parties have forgotten how to count.